Fluid catalytic cracking process for heavy oil

Abstract

A heavy fraction oil is catalytically cracked by contacting the oil with a catalyst mixture consisting of 60 to 95 wt % of a base cracking catalyst containing an ultra stable Y-type zeolite and less than 0.5 wt % of rare-earth metal oxide, and 5 to 40 wt % of an additive containing a shape-selective zeolite, in a fluid catalytic cracking apparatus under conditions that a reaction zone outlet temperature is in the range of 580 to 630° C., the catalyst/oil ratio is in the range of 15 to 40 wt/wt, and the contact time of hydrocarbons in the reaction zone is in the range of 0.1 to 1.0 seconds, wherein the yield of light-fraction olefins can be enhanced.

What is claimed is:  
     
       1. A process for the fluid catalytic cracking of a heavy-fraction oil, which comprises 
       contacting the oil with a catalyst mixture consisting of 60 to 95 wt % of a base cracking catalyst containing an ultra stable Y-type zeolite having a crystal lattice constant of greater than 24.55 Å to 24.60 Å, and less than 0.5 wt % of rare-earth metal oxide, and 5 to 40 wt % of an additive containing a shape-selective zeolite; said additive having a bulk density of 0.5 to 1.0 g/ml, an average particle diameter of 50 to 90 microns, a surface area of 10 to 200 m 2 /g and a pore volume of 0.01 to 0.3 ml/g;  
       wherein said contacting takes place in a fluid catalytic cracking apparatus having a regeneration zone, a down flow reaction zone, a separation zone and a stripping zone, and under conditions that the reaction zone outlet temperature is in the range of 580 to 630° C., the catalyst/oil ratio is in the range of 15 to 40 wt/wt, and the contact time of hydrocarbons in the reaction zone is in the range of 0.1 to 1.0 sec.  
     
     
       2. The process according to  claim 1  wherein the reaction zone outlet temperature is in the range of 590 to 620° C. 
     
     
       3. The process according to  claim 1  wherein the contact time of hydrocarbons in the reaction zone is in the range of 0.2 to 0.7 seconds. 
     
     
       4. The process according to  claim 1  wherein the fluid catalytic cracking apparatus is operated at the reaction pressure of  1  to 3 kg/cm 2 G. 
     
     
       5. The process according to  claim 1  wherein the fluid catalytic cracking apparatus is operated with the catalyst/oil ratio of 20 to 30 wt/wt. 
     
     
       6. The process according to  claim 1  wherein the rare-earth metal oxide content in the base cracking catalyst is less than 0.3 wt %. 
     
     
       7. The process according to  claim 1  wherein the rare-earth metal oxide content in the base cracking-catalyst is less than 0.1 wt %. 
         8 .The process according to  claim 1  wherein the zeolite content in the base cracking catalyst is in the range of 5 to 50 wt %. 
     
     
       9. The process according to  claim 1  wherein the zeolite content in the base cracking catalyst is in the range of 15 to 45 wt %. 
     
     
       10. The process according to  claim 1  wherein the shape-selective zeolite contained in the additive is ZSM-5. 
     
     
       11. The process according to  claim 1  wherein the shape-selective zeolite content in the additive is in the range of 20 to 70 wt %. 
     
     
       12. The process according to  claim 1  wherein the shape-selective zeolite content in the additive is in the range of 30 to 60 wt %. 
     
     
       13. The process according to  claim 1  wherein the shape-selective zeolite is selected from the group consisting of ZSM-5, omega, SAPO-5, SAPO-11, SAPO34 and pentasil aluminosilicates.